In general, a cutting tool is used in cutting operations for cutting workpieces of various materials, and usually designed to be mounted on a machine tool to carry out a cutting operation for cutting a workpiece in a desired shape.
Such a cutting tool includes a cutting insert having several cutting edges adapted to directly carry out a cutting operation and a cutter body for holding and clamping the cutting insert.
In general, methods for cutting a metal workpiece with such a cutting tool can be divided into two methods, i.e., a method for cutting a rotating workpiece with a stationary cutting tool and a method for cutting a stationary workpiece with a rotating cutting tool.
A milling process belongs to the latter method, and the milling process includes plane machining, side machining, slot machining, hole machining or the like with a milling cutter.
In an effort to reduce cutting resistance, increase the expected life span of a cutting tool and improve the machining quality during the cutting process using a milling tool, an improved shape of the insert and the structure combined with the cutter body has been recently, actively studied and developed. Among the efforts, various efforts to achieve right angles between side faces and a bottom face of the machined workpiece, in the cases of side machining and slot machining, have been proposed.
In Korean Patent Laid-open publication No. 97-61414, a cutting insert is disclosed wherein the respective cutting edges become convex toward their middle planes as viewed in plan, and inclined downwardly toward their middle planes as viewed in side elevation. The cutting insert, is clamped on a cutter body to reduce the cutting resistance and to achieve a right angle between a side face and a bottom face of the machined workpiece, in the case of a side machining.
In the case of the above-mentioned cutting insert, a milling tool is used in which the cutting edges become convex toward their middle planes as viewed in plan and the cutting insert is clamped on the cutter body. Therefore, the right angularity of the machined side surface, i.e., the right angularity between the side faces and the bottom faces of the machined workpiece, can be partially improved but cannot be perfectly achieved in the case of slot machining or side machining. Furthermore, though it is possible to reduce the cutting resistance one to an increase of the radial oblique angle by being clamped on the cutter body, and the cutting resistance can be reduced by an increase of the axial oblique angle, when a workpiece is machined to a depth of one-half or less of the cutting edge width, the cutting resistance is reduced by a decrease of the axial oblique angle in the case of being machined to a depth of one-half or more of the width.
In another publication, U.S. Pat. No. 5,199,827, there is disclosed a cutting insert having cutting edges adapted to cut a portion of a workpiece in the shape of a right angle, in the case of side machining.
In practice, the optimal machining right angularity can be obtained only in the case of having twisting cutting edges, as in an end mill of the integral or soldered type, in order to form a machined surface having an exact right angle. However, the cutting insert has straight cutting edges, a flatness of a side machined by the straight cutting edges is not effective than that machined by the twisting cutting edges. Also, since it is possible to achieve increase of the radial inclined angle and the axial inclined related to the cutting resistance when being clamped on a cutter body, the cutting resistance can be reduced.